Edexcel FD2 2020 June — Question 5

Exam BoardEdexcel
ModuleFD2 (Further Decision 2)
Year2020
SessionJune
TopicNetwork Flows

5. \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{e0fc09f9-06ea-4528-a2de-f409112d85cc-06_830_1397_205_333} \captionsetup{labelformat=empty} \caption{Figure 2}
\end{figure} Figure 2 shows a capacitated, directed network. The network represents a system of pipes through which fluid can flow. The weights on the arcs show the lower capacities and upper capacities for the corresponding pipes, in litres per second.
  1. State the source node.
  2. Explain why the sink node must be G.
  3. Calculate the capacity of the cut \(C _ { 1 }\)
  4. Assuming that a feasible flow exists,
    1. explain why arc JH must be at its upper capacity,
    2. explain why arcs AD and CD must be at their lower capacities.
  5. Use Diagram 1 in the answer book to show a flow of 18 litres per second through the system.
  6. Prove that the answer to (e) is the maximum flow through the system.